1 . Field of the Invention
The present invention relates to a bending device that bends a bending section by towing of a wire and to an endoscope.
2 . Description of the Related Art
In recent years, a medical instrument inserted into a subject, for example, an endoscope, has been widely used in a medical field. The endoscope can perform observation, treatment, and the like of a region to be examined in the subject by inserting an elongated insertion section into the subject.
A configuration is well-known in which a bending section bendable in a plurality of directions configuring a bending device is provided in the insertion section of the endoscope.
The bending section improves progression of the insertion section in a bent section in a conduit and changes, in the insertion section, an observation direction of an observation optical system provided in a distal end portion concatenated to a distal end in a longitudinal axis direction (hereinafter simply referred to as distal end) of the insertion section in the bending section.
Usually, a plurality of bending pieces are coupled by rivets or the like along the longitudinal axis direction of the insertion section, whereby the bending section is configured to be bendable in, for example, upward, downward, left, and right four directions.
More specifically, any one of four wires inserted to be movable to a front and a back in the longitudinal axis direction (hereinafter simply referred to as the front and the back) in the insertion section and configuring a bending device, a distal end of which fixed to the bending piece located on a most distal end side in the longitudinal axis direction (hereinafter simply referred to as distal end side) among the plurality of bending pieces, is towed using a bending operation knob of an operation section, whereby the bending section is bendable in any one of the upward, downward, left, and right directions. Note that the four wires are inserted while being shifted, in the bending piece, from one another in a circumferential direction of the bending piece by approximately 90° along an inner circumferential surface of the bending piece.
On inner circumferential surfaces of the plurality of bending pieces, the four wires are inserted along the longitudinal axis direction, whereby wire receivers configuring the bending device that hold the respective wires to be advanceable and retractable in the longitudinal axis direction along the inner circumferential surfaces of the plurality of bending pieces are provided while being shifted from one another in the circumferential direction by approximately 90° for each of the wires. The respective wire receivers hold the respective wires such that the respective wires do not shift in the circumferential direction and a radial direction of the bending pieces.
A configuration is also well-known in which the bending section provided in the insertion section of the endoscope is configured from a first bending section and a second bending section concatenated to a proximal end in the longitudinal axis direction (hereinafter simply referred to as proximal end) of the first bending section.
In such a configuration, the respective distal ends of the four wires are fixed to a distal end of the first bending section. In the second bending section, coil sheathes, distal ends of which are fixed to a distal end of the second bending section and proximal ends of which are switchable to a fixed state and an unfixed state, are respectively covered on outer circumferential of the respective wires.
If the proximal ends of the respective coil sheathes are fixed, when any one of the four wires is towed, the respective coil sheathes resist a compression force applied in the longitudinal axis direction. Therefore, only the first bending section is bent. If the proximal ends of the respective coil sheathes are not fixed, when any one of the four wires is towed, the second bending section bends in the same direction with the first bending section.
Note that, in the second bending section, coil sheathes formed by densely winding four element wires are inserted through the respective wire receivers along the longitudinal axis direction.
Consequently, the respective wire receivers hold the respective coil sheathes to be advanceable and retractable in the longitudinal axis direction along the inner circumferential surfaces of the plurality of bending pieces. More specifically, the respective wire receivers hold the respective wires such that the respective coil sheathes do not shift in the circumferential direction and the radial direction of the bending pieces.
When the bending section is bent, when any one of the four wires is towed, the towed wire is pressed against the inner circumferential surfaces of the plurality of bending pieces that bend in one direction.
This is the same when the coil sheathes are provided in the insertion section. When the second bending section is bent with the first bending section, the coil sheathes are pressed against the inner circumferential surfaces of the plurality of bending pieces configuring the second bending section that bends in one direction.
As a result, the wires and the coil sheathes are pressed against the respective wire receivers located while having a set interval along the longitudinal axis direction. Large forces are locally generated in contact places of the wires and the coil sheathes with the respective wire receivers. That is, large sliding resistance is locally generated.
Therefore, a problem arises that a force amount for towing the wires increases, that is, not only an operation force amount of the wires increases but also the wires and the coil sheathes are easily worn.
In view of such a problem, Japanese Patent Application Laid-Open Publication No. 2009-78012 discloses a configuration in which coil springs including sparsely wound regions and densely wound regions are respectively covered on outer circumferences of respective wires inserted through a bending section respectively, whereby, when the wires are towed, the wires are prevented by the coils springs from being directly pressed against wire receivers.
Note that, since the coil springs can also be covered on the outer circumferences of the coil sheathes, in the configuration in which the bending sections include the first bending section and the second bending section, if the coil springs are used, it is also possible to prevent, with the coil springs, the coil sheathes from being directly pressed against the wire receivers.